ball valves are often classified as either top entry ball valves or side entry ball valves. A side entry ball valve is generally characterized in that a portion of the valve body on either the inlet or outlet side of the valve can be removed in order to install and/or remove a ball flow control member into or from a ball chamber inside the valve body. Generally, if it is required to remove or install the ball from the ball chamber, this design requires the ball valve to be disconnected and removed from any process components, such as pipes or other components, so that the side of the valve can be removed. However, this makes it difficult, if not impossible, to remove and/or insert the ball while the side entry ball valve is installed in-line in the field.
In contrast, a top entry ball valve is generally characterized in that the ball may be installed into and/or removed from the ball chamber through an opening in a top wall of the valve body which is spaced between the inlet side and the outlet side of the valve body. Because the inlet and outlet sides of the valve body are not disturbed, it is possible to access the ball inside the ball chamber without removing the top entry ball valve from an installed in-line position in the field. In some instances, this can make it easier to service a top entry ball valve when installed in-line in the field.
However, in some arrangements a top entry ball valve may require special equipment in order to install and/or remove the ball from his operative position inside the valve body. For example, a floating ball valve often has a ball that is compressed between two valve seats by spring in such manner that the valve seats retain the ball in an operative position while the ball can simultaneously be rotated between open and/or closed positions. Frequently, the spring generates a large compression force, such as five hundred pounds force, one thousand pounds force, or possibly even more, in order to retain the ball in its operative position. A trunnion ball valve may in some arrangements also include a spring arranged to press against the ball under similar compression forces. For either of these types of ball valves, it is common to have special tools and/or procedures for retracting the spring in order to be able to remove and/or insert the ball due to the relatively high compression forces generated by the spring.